Include current post into loop

I have a related posts loop ( in every single post page ) based on post title. source : https://wpza.net/get-related-posts-based-on-the-posts-content-in-wordpress/

But I also need to include current post into this loop 'post__in' = $similar, . Please can anyone help me how can I do this

function custom_related_posts() {
     $current_id = get_the_ID();
      $current_content = get_the_title( $current_id );
     $similar = array();
     $scores = array();
     $percentage = 0;
     $output = '';

     function compare_content( $current_content, $comparison_content ) {
          $current_content = trim( strtolower( $current_content ) );
          $comparison_content = trim( strtolower( $comparison_content ) );
          similar_text( $current_content, $comparison_content, $percentage );
          $formated_percents = number_format( $percentage );
          return $formated_percents; 
     }

     $args = array(
          'post_type' = 'product',
          'posts_per_page' = -1
     );
     $loop = new wp_query( $args );
     while( $loop-have_posts() ) {
          $loop-the_post();
           $score = compare_content( $current_content, get_the_title() );
          if ( $score  90  get_the_ID() != $current_id ) {
               array_push( $similar, get_the_ID() );
               array_push( $scores, $score );
          }
     }
     wp_reset_query();

     array_multisort( $scores, SORT_NUMERIC, SORT_DESC, $similar );

     if ( ! empty( $similar ) ) {
          $args = array(
               'post_type' = 'product',
               'posts_per_page' = 100,
               'post__in' = $similar,
               'orderby' = 'meta_value_num',
'order' = 'asc',
'meta_key' = '_price'
          );
          $loop = new wp_query( $args );
          $i = -1;
          while ( $loop-have_posts() ) {
               $loop-the_post();
               $i++;
               echo do_shortcode('[wbcr_snippet id=22379]') ; echo  'div class=ai'. $scores[$i] .'% oxsar mehsul/div'; 
          }
          wp_reset_query();
     }
     return $output;
}